J. Raptor Res. 28(2):100-107 ¸ 1994 The Raptor ResearchFoundation, Inc. BEHAVIOR AND ACTIVITY OF REHABILITATED BUZZARDS (Buteo buteo) RELEASED IN NORTHERN ITALY DAVIDE CSERMELY AND CARLO VITTORIO CORONA 1 Dipartimentodi Biologiae FisiologiaGenerali, Universitd di Parma, Viale delle Scienze,1-43100 Parma, Italy AI•STI•CT.--The behaviorand habitat huntingof 16 rehabilitatedcommon buzzards (Buteo buteo) released in northernItaly were analyzed.The buzzardswere releasedindividually in differentseasons, and their activitywas recorded continuously for at leastthe first 3 d after releaseand intermittently thereafter until they dispersedfrom the releasesite. The birds remainedin the surroundingarea for more than 100 d, showinga progressiveacclimation to the new environment.The releasedbuzzards interacted frequently with wild territorialconspecifics and were attackedby severalspecies of corvids,especially the hooded crow (Corvuscorone). Nevertheless, such interactions were not the directcause of dispersal.Some birds defendeda territoryadjacent to or insidethat of a wild buzzard.Prey capture was almost normal, although certainlyunderestimated. Small mammalsand reptileswere mostoften caught. Although the area chosen for this studyhad high human population,this was not a major sourceof interferencewith the releases. Thus,the buzzards appeared to be ableto copewith theirnew environment being minimally influenced by havingbeen in captivity. KEY WORDS: hawks;Buteo buteo; behavior; captivity; dispersal,' rehabilitation; behavioral ecology. Comportamientoy actividad de los Buteobuteo rehabilitados y deyadosen libertaden el nordede Italia RESUMEN.--Seanaliz6 la conductay el habitatde caza de 16 individuosrehabilitados de la especieButeo buteo liberados en el norte de Italia. Los individuos de B. buteo fueron liberados en el firea de estudio individualmenteyen diferentesestaciones; su actividadfue registradacontinuamente por al menostres dias despugsde su liberaci6ne intermitentementehasta el momentode abandonarel sitio de liberaci0n. Las avespermanecieron en los alrededoresdel firea por mils de 100 dias,mostrando una progresiva aclimataci0nal nuevoambiente. Los individuos liberdos interactuaban frecuentemente con conespecificos territorialessilvestres y fueronatacados por variasespecies de c6vidos,especialmente Corvus corone. Sin embargo,tales interacciones no fueronla causadirecta de su dispersion.Algunas aves defendieron territoriosvecinos o al interiorde losdefendidos por individuossilvestres. La capturade presafue casi normal,aunque ciertamente subestimada. Tanto pequefiosmamiferos como reptiles fueron a menudo capturados.Aunque las fireasescogidas para esteestudio tenlan una alta poblaci6nhumana, este factor no constituy6una gran fuente de interferenciassobre las liberaciones. En slntesis,B. buteoparece ser capazde incertarseen sunuevo mediambiente siendo escasamente influenciado por su cautividad. [Traducci6n de Ivan Lazo] Severalprograms for the rehabilitationof raptors still neglected.In fact, it is almostimpossible to get have been developedin recentyears by institutions information of the fate of released birds from the devotedto the protectionof birds. Standard proce- literature, because most data refer to survival rate dures for raptor rehabilitation have been developed and recoverydistance from the releasesite (Servheen for severalspecies (Nelson 1977, Llewellynand Brain and English 1979, Duke et al. 1981, Ingram 1983, 1983, Pendletonet al. 1987, Weaver and Cade 1991) Hamilton et al. 1988). Moreover, little precisein- as well as the techniquesfor successfulrelease (Shet- formation has been compiledon the behaviorof in- rod et al. 1982, Llewellyn 1991). Nevertheless,the dividuals after release. adaptationof birds back into the natural habitat is The objectiveof this study was to fill that gap, investigatingin detail the behavior,activity, and in- tra- and interspecificinteractions in a group of com- • Present address: Via P. Petronia 89, 1-00136 Roma, mon buzzards(Buteo buteo) immediately after re- Italy. lease following rehabilitation until they dispersed 100 JUNE 1994 BEHAVIOROF RELEASEDBUZZARDS 101 from the area. Such an investigationis likely to be The daylight period was equally dividedinto three sec- of interestto raptor rehabilitators(Meyers and Mil- tions that were variable during the year based upon the ler 1992). photoperiod.The proportionof time spentin eachhabitat for each one-third of the daylight period and in every METHODS seasonwas arcsintransformed for comparison.The exact time of sunriseand sunsetfor the geographicalcoordinates The buzzardsused in this study were all wild birds, of the area were calculatedevery 2 wk. The days after housedtemporarily for rehabilitation at the Raptor Re- releasewere countedconsidering the day of releaseas day habilitationCentre (RRC) managedby the Italian Society one. The days of the year were indicatedconsidering the for the Protectionof Birds (LIPU) near Parma. They all spring equinox as day zero. originatedin northernor centralItaly within 100-200 km We usedthe Mann-Whitney U-test to comparemeans, of the release area. When released the birds were all in the Kruskal-Wallis one-way ANOVA (Siegel 1956) to perfect physical condition and flying fitness, and were evaluate time durations between seasons or between thirds chosenrandomly amongthose ready for releasing.Those of the day, the Spearman rank correlationto ascertain possiblyimprinted to humans were not considered. possiblecorrelations, and the Chi-square test to compare A total of 16 buzzards were studied. Six were adult frequencies.The means are given ___SE, and the proba- (two males and four females) and 10 were sub-adults (five bility is always given as two-tailed. malesand five females).They were releasednear the end of each season,from April 1990 to November 1991. Five RESULTS were studied between winter and spring, four between spring and summer, three between summer and autumn, Most buzzardsdid notdisappear quickly from the and four between autumn and winter. Thus, we avoided releasesite in 426.6 hr of observation(Table 1). The the most stressfulclimatic conditionsthat occur in Janu- area used by the birds was about 2730 ha in size, ary-February and in July-August (Kostrzewaand Kos- almost centered around the release site. One-half of trzewa 1991). The duration in captivity was variable, the sampledbuzzards left the studyarea within three ranging from a few days to severalmonths, depending on the seriousnessof the injury or illness.The mean duration days. Three departed within a few hours and one for nine buzzards was 295.5 + 109.2 d. We did not know on day three. This occurredin early spring and the period for the other five, but it was certainly within autumn. the same range. Mortality. Three buzzardsdied in the studyarea The release site was located within a waterfowl sanc- by electrocutionafter perching on medium-tension tuary managedby LIPU about 15 km north of Parma and 5 km from the Po River. The area is flat and without pylonswhich are widely distributedin the plains of extensivewoodlands but with a high human population Italy, and unfortunatelyare a seriousproblem for density. The site was chosenbecause of the necessityto otherspecies too. One bird diedof a gunshotwound observeclosely and track the buzzard behavior precisely, receivedduring the night or at dawn beforewe start- even for long distancesif necessary.Wild buzzards are regularly presentparticularly during winter. Severaltaxa edour observationsession, and anotherdied in spring of invertebratesand terrestrialvertebrates offered an easy for unknownreasons during a late snowfall.Finally, and variable food source. one buzzard was recaptured closeto starvation. The area surroundingthe releasesite containedseveral Habitat Use. Habitat typeswithin the studyarea biotopes,with rather differing vegetalcover. The habitat typeswere evaluatedusing the methoddescribed by Emlen were small. Their distributionwas almostregular, (1956). Several watercourses--the Parma River and sev- andthe buzzardsmoved very easilyfrom onehabitat eral streams--run within the studyarea. Most of the trees to another.We foundgreat individual variability in are concentratedalong them. habitat use (H = 31.79, N = 450, P < 0.001, mea- The buzzardswere releasedindividually between 0900- suredas minutes spentby eachbird in eachhabitat). 1500 H on days without precipitation.Beforehand they were kept on locationin an outdoor aviary for 1-2 wk in Birdsthat changedhabitat frequently had beenkept order for them to habituateto the environment.A radiotag in captivity for the least time (Z = 2.18, N = 279, (9 g two stage,BIOTRACK, Wareham, U.K.) was at- P < 0.05). During winter, buzzardsstayed in one tached some hours before release (Kenward 1987, White habitat longer than in other seasons,both during and Garrott 1990). days 1-3 (H = 10.28, N = 390, P < 0.05) and in The buzzardswere followed virtually continuouslyfrom dawn to dusk each day if weather permitted for the first all-days (H = 17.58, N = 485, P < 0.001). 3 d after release, hereafter referred as "days 1-3." If a The buzzards remained longer in open habitats bird did not leavethe area, it was subsequentlymonitored than in areaswith thick vegetationin every period intermittentlywith the sameschedule at 1-4 d intervals, considered(Kostrzewa 1989). The tendencyto ex- until the bird disappearedfrom the surroundings.That period, including the first 3 d, is hereafter indicated as plore different habitats immediately after release, "all-days."